Wooden battery separator



Patented June 7', 1927.

UNITED STATES PATENT OFFICE.

ELIE s. uMnoLn'r, or OAKLAND, CALIFORNIA, ssIG oR 'ro'rirn PACIFIC LUMBER COMP NY, or sAN FRANCISCO, CALIFORNIA, A CORPORATION or MAINE.

a No Drawing.

This invention relates to the chemical treatmentrof wood to adapt it for use as storage battery separators, as well as to the roducts of the treatment includin a retreated wooden blank adapted forsimple shaping for use in the battery. I

The objects of the treatment are 1st, to remove from the wood as much as possible the deleterious constituents ofthe ligno-cellulose which may otherwise become hydrolized or oxidized by the battery ment already treated to the battery separator manufacturer,-something not practicable heretofore on account of wood treated in the ordinary way having a tendency to split if subject to mechanical handling.

' The above objects'are best secured by my process treating the wood whi-legre'en, preferably at the mill where it-is produced, for

Iihave found-that'no t only is the extraction quicker and more even, but results in an entirely difierent product, so very much more pliable and tougher, both before and after drying, that it becomes perfectly feasi ble as a commercial undertaking to manufacture and chemically pretreatthe separator blanks or slabs at the mill and ship them either moist or dry to the battery separator maker for subsequent grooving and finishing to exact dimensions to produce the final separator ready for use in the battery.

This gain in toughness and pliability through treatment of the green wood is a very important feature and probably due to avoidance of any change, hardening, or oxidation of the extractive matter or. associated tissue ordinarily produced in drying, for once the wood is dried and then treated there is a marked lowering of its to form the finished separatorreaoly' woonEN BATTERY sEPAnATon.

Application filed August 28, 1924.-- Serial No. 734,815.

pliability and toughness'which greatly increases liability of breakage and splitting, and which has prevented the commercial quantity preparation of battery separator blanks or slabs atthe mill, and the Wood has always'been reduced to exact size, and surfaeegrooved, by the battery maker, and then variously chemically treated after all mechanical work was done. 7 e I My process of treatment is as follows The green wood, is first cut into thin slabs of a thickness corresponding to that ofthe unfinished separator, generally about one sixteenth of an inch, and of a superficial area a trifle larger than the required separator, or in multiples there-of.

The slabs are then leachedin water, either hot or cold, as may best suit the specie of the wood being used,to extract thesoluble extractive matter, after which the slabs are treated in a hot solution of either an alkali sulphite or of an alkali bisulphite; the sodiumsalts are generally to be preferred because they are cheap, effective, and do not leave insoluble compounds in the fiber of the wood. V

A solution of the salt of from 5 to 12% applied at or nearthe boiling point for a duration of from 5 to lO hours will generally yield satisfactory results; however, the'best concentration and the time of treatment will vary considerably with the kind of wood being treated, and also depend-on its age and lig'nification, therefore I do not wish to limit myself to any definite concentration or duration of treatment. A few experiments with a particular kind of wood will easily determine the best way of applying my treatment.

When the reaction has been carried to completion, the wooden strips or slabs are immediately washed, preferably in warm water until they are free from both the reagent as well as the reaction products. After washing the slabs may either be partially dried for shaping and finishing,'or dried completely for shipping or storing, taking care to preserve the flatness of the slabs during the drying process.

The washing can generally be shortened by first rinsing the slabs thoroughly and then soaking them for a short time in warm water slightly acidulated (about 1%) with sulphuric acid to destroy the last trace of sulphite held by the wood fiber.

The resulting sodium sulphate being soluble easily passes out in the washing.

It must be observed that the use of neutral sulphite is more suitable for the treatment of young and soft woods; while the bisulphite, being more energetic, is to be preferred for the older and harder woods, but the use of bisulphite is more liable to yield products which dry hard and brittle unless the action is stopped in time and the final washing done thoroughly.

The finished slab is characterized by its suppleness and its porosity, as the lignocellulose of the hard or winter growth appears to be attacked more deeply than the summer growth, with the result that the wood after treatment has a more even structure than the original material, and also shows a considerable gain in toughness, with less liability of splitting in the subsequent grooving and finishing to the exact separator size.

I claim 1. The process of treating wood for battery separators which comprises reducing the wood while green to substantially the thickness of the desired separators, soaking the green slabs in an aqueous solution of a sullite or bisulfite at temperatures ranging from 15 C. to the boiling point, and washing out the excess of reagent.

2. The process-of treating Wood for; battery separators which comprises reducing the wood while green to substantially the thickness of the desired separators, soaking the green slabs in an aqueous solution of a sulfite or bisulfite at temperatures ranging from 15 C. to the boiling point, washing out the excess of the reagent and thereafter drying the wood.

3. The process of treating wood for battery separators which comprises reducing the wood while green to substantially the thickness of the desired separators, soaking the green slabs in an aqueous solution of asulfite or bisulfite, treating with acidulated water, and washing.

4. The process of treating wood for battery separators which comprises reducing the wood while green to substantially the thick-- ness of the desiredseparators, soaking the green slabs in an aqueous solution of a sulfite or bisulfite, treating them with acidulated water, washing, and drying.

5. The process of treating wood for battery separators which comprises reducing the wood while green to slab form suitable for cutting therefrom of the desired separators, of chemically treating the slabs while green to remove the deleterious lignone con tent to adapt the slabs for battery use, and of drying the treated slabs for subsequent mechanical reduction to exact form for use in the battery. v

6. The process of treating wood for battery separators which comprises reducing the wood while green to slab form suitable for cutting therefrom of the desired separators, of chemically treating the slabs while green to remove the deleterious lignone content to adapt the slabs for battery'use, drying the slabs, and thereafter reducing the slabs mechanically to exact sizeand form for battery use. v i V 7. An article of manufacture comprising wooden slabs for battery separators chemically treated while green to remove the deleterious lignone content, and adapted to further mechanical reduction to exact size for the separators. V

8. An article of manufacture comprising wooden slabs for battery separators chemically treated while green to remove the deleterious lignone content, and adapted for further mechanical reduction to exact size for the separators without further chemical treatment. I

9. An article as specified in claim 7 in which the slabs are each of a superficial area larger than the required finished separator."

ELIE S. HUMBOLDT. 

